Flow battery capacity recovery method and device and application thereof

Abstract

The invention relates to a flow battery capacity recovery method and device and application, and particularly relates to the technical field of flow batteries. An existing electrolyte capacity recovery method has certain defects and cannot meet the requirements of effectiveness, safety, convenience, economical efficiency and environmental friendliness at the same time, and according to the capacity recovery method of the flow battery electrolyte, a reduction battery and a rebalance battery are constructed; the positive electrode electrolyte of the redox flow battery is reduced only by consuming electric energy and water, the reaction process is mild and safe, active substances playing a reducing role can be recovered through charging, and cyclic utilization of the reducing active substances is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a liquid flow battery capacity recovery method, a device and an application thereof. Background Art

[0002] As the installed capacity of new energy sources such as wind power and photovoltaic power continues to break records and exceed the installed capacity of thermal power, the proportion of new energy applications will continue to increase in the future. The intermittent characteristics of wind power and photovoltaic power inevitably require matching energy storage equipment of corresponding scale. In the case that the safety of lithium batteries has not been resolved, liquid flow batteries, as safe, easy to prepare on a large scale, and cost-controlled energy storage batteries, will inevitably assume the responsibility of large-scale energy storage, which will place high demands on the use and maintenance of liquid flow batteries.

[0003] Conventional flow batteries that have entered the energy storage market include all-vanadium flow batteries, iron-chromium flow batteries, and zinc-bromine flow batteries. Among them, all-vanadium flow batteries and iron-chromium flow batteries have developed particularly rapidly in recent years. During the long-term use of all-vanadium flow batteries and iron-chromium flow batteries, R&D and maintenance staff found that with the periodic circulation of flow batteries, the electrolyte of the flow battery will show a trend of capacity decay due to hydrogen evolution, and this capacity decay will continue to accumulate with the increase in the number of charge and discharge cycles until it has a significant impact on the charge and discharge time of the energy storage system. This capacity decay is caused by the imbalance of active ion concentration in the positive electrode electrolyte caused by hydrogen evolution at the negative electrode of the flow battery during charging. Therefore, the process of capacity recovery of the flow battery electrolyte is to adjust the active ion concentration of the positive electrode electrolyte and reduce the active ions in the positive electrode electrolyte to their normal valence state.

[0004] The commonly used methods for restoring electrolyte capacity include the following. The first recovery method is to add an appropriate amount of reducing agent to the positive electrode electrolyte. These reducing agents react with the active ions in the positive electrode electrolyte to reduce the unbalanced ions to normal valence states. At the same time, these reducing agents themselves are oxidized to generate ions, gases or water and other components that do not affect the charge and discharge reactions of the flow battery. The existing reducing agents include organic small molecules involved in patents CN202310659813.0 and CN202311743091.3; ammonium ferrous sulfate involved in patent CN201510927447.8; polymerized organic molecular spheres involved in patent CN201911034854.0, etc. The second recovery method is to use hydrogen to carry out an oxidation-reduction reaction with the high-valent ions of the positive electrode to reduce these high-valent ions to a normal valence state, such as the oxidation-reduction reaction of hydrogen with pentavalent vanadium ions and trivalent iron ions introduced in patents CN202211332184.2, CN202311526514.6, and CN201920744613.4 to reduce pentavalent vanadium ions and trivalent iron ions to a normal valence state. The third recovery method is to introduce the positive electrode electrolyte into a special electrolytic cell, place the positive electrode electrolyte at the negative electrode of the electrolytic cell, and then power on the electrolysis to reduce the high-valent ions of the positive electrode electrolyte, such as the electrolysis of the positive electrode electrolyte of the all-vanadium liquid flow battery introduced in patent CN202210059757.2 to reduce it to a normal valence state.

[0005] However, the above three methods for recovering electrolyte capacity all have defects. The first recovery method requires adding a reducing agent to the positive electrode electrolyte, which will not only bring reducing agent residues into the electrolyte, but also the by-products after the reaction will remain in the electrolyte. These reducing agents and by-products may affect the charge and discharge performance of the flow battery and the overall performance of the flow battery; in addition, the flow battery needs to add reducing agents from time to time throughout its life cycle. These operations are not only cumbersome and risky, but the consumption of these reducing agents is a cost that cannot be ignored during the operation of the flow battery, resulting in an increase in the operation and maintenance costs of the flow battery. The second recovery method requires hydrogen to participate in the electrochemical reaction, and requires the use of expensive catalysts. This will not only increase the operational risk of this method due to the transmission of hydrogen involved in the operation process, but also because the catalyst has a service life problem, it is necessary to replace the catalyst or replace the reaction battery from time to time, resulting in high complexity and high operating costs of this method. The third recovery method requires the use of special electrolytes to participate in the electrolytic reduction of the positive electrolyte of the flow battery. In the process of electrolysis, these special electrolytes will be continuously consumed and by-products will be continuously produced. These by-products may be acidic gases, so special acid removal equipment and acid removal chemicals are required to deal with them. This not only increases the danger of the entire electrolytic reduction operation, but also leads to an increase in the cost of the entire process.

[0006] The above three existing electrolyte capacity recovery methods all have certain defects and cannot meet the requirements of effectiveness, safety, convenience, economy and environmental friendliness at the same time. They are not suitable for large-scale application of liquid flow batteries in the future. Therefore, at this stage, liquid flow batteries urgently need an effective electrolyte capacity recovery method that does not affect the use of liquid flow batteries and is safe, simple and low-cost. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a new method for recovering the electrolyte capacity of a flow battery, which is specifically implemented by the following technical solutions:

[0008] Step 1: Charge the flow battery that needs to recover capacity, test the valence state of the positive electrolyte ions before and after charging, and calculate the total amount of ions that need to be restored and the total charge transfer number for rebalancing as the design capacity;

[0009] Wherein, the liquid flow battery is selected from one of an all-vanadium liquid flow battery, an iron-chromium liquid flow battery or a zinc-bromine liquid flow battery.

[0010] Among them, the valence state of the positive electrode electrolyte ions is tested by potentiometric titration. The specific steps are as follows: (1) Take an appropriate amount of electrolyte for potentiometric titration; (2) When the potential suddenly changes, stop the titration and record the consumption of the titrant at this time; (3) Calculate the concentration of active ions of corresponding valence state in the electrolyte, and calculate the total amount of charge required to transfer for rebalancing as the design capacity.

[0011] Step 2: Construct a reduction battery: The positive and negative electrodes are made of stable acid-resistant materials, and the positive and negative electrodes are connected. The positive and negative electrolytes have the same composition, the electrolyte is an acidic electrolyte, the electrolyte contains a redox medium, and the solvent is water;

[0012] Wherein, the acid-resistant material is selected from one of platinum, palladium, silver, titanium, nickel, graphite, carbon nanotubes, diamond film, titanium oxide, nickel oxide, tin oxide, or a composite material composed of any two of the above;

[0013] The third step: charging the reduction battery. Connect the positive and negative electrodes of the DC power supply to the positive and negative electrodes of the reduction battery respectively, and power on for electrolysis. Oxygen is released at the positive electrode, and the redox medium on the negative electrode undergoes a reduction reaction. When the total amount of charge transfer reaches the above-mentioned design capacity, the electrolysis is stopped.

[0014] Step 4: Build a rebalancing battery, use the positive and negative electrodes of the reduction battery after charging or the same materials as the positive and negative electrodes of the reduction battery after charging as the positive and negative electrodes of the rebalancing battery, the electrolyte of the reduction battery after charging is used as the negative electrolyte of the rebalancing battery, and the positive electrolyte of the flow battery after charging is used as the positive electrolyte of the rebalancing battery. The positive and negative electrolytes are separated by a proton exchange membrane.

[0015] Step 5: Discharging the rebalanced battery. Connecting the discharge device to the rebalanced battery to discharge the rebalanced battery. When the total amount of charge transfer during the discharge of the rebalanced battery reaches the designed capacity, the discharge is stopped until the valence state of the positive electrode electrolyte is restored to the initial state.

[0016] Step 6: The capacity of the liquid flow battery is restored by introducing the positive electrode electrolyte of the rebalanced battery after discharge into the positive electrode of the liquid flow battery.

[0017] After the cycle is completed, the difference between the liquid level in the positive and negative electrode storage tanks of the flow battery and the initial state is calculated to determine whether deionized water needs to be added to the positive and negative electrode storage tanks.

[0018] The redox media in the second step need to be a simple substance or compound with appropriate reducing properties, and do not react with other components in the electrolyte of the flow battery except the redox media, the redox potential is lower than the positive electrode potential of the flow battery to be reduced, the redox product will not penetrate the proton exchange membrane in the rebalancing battery, and have little effect on the charge and discharge reaction of the flow battery. Specifically, it can be selected from zinc, nickel, lead, anthraquinone, violacene, ferrocene, etc., and the above substances can be designed with their own specific recovery methods according to the above process according to their own characteristics.

[0019] The redox mediator is selected from Zn / Zn 2+ ,Ni / Ni 2+ 、Pb / Pb 2+ 、AQDSH2 / AQDS、EV 0 / EV 2+ Or one of FcNNO3(FeⅡ) / FcNNO3(FeⅢ).

[0020] The molar concentration of the redox medium in the electrolyte is 0.001-5 mol / L;

[0021] Preferably, the molar concentration of the redox medium in the electrolyte is 0.005-3 mol / L.

[0022] The redox medium can be recycled after the rebalanced battery is discharged.

[0023] The entire electrolyte capacity recovery process mentioned above is a process of continuously generating oxygen, and the generated oxygen escapes into the air; in addition, since the hydrogen generated during the charge and discharge process of the flow battery is generally discharged from the flow battery into the air, the water in the electrolyte will be continuously consumed during the operation, maintenance and electrolyte capacity recovery of the flow battery. Therefore, after the electrolyte capacity recovery process is completed, deionized water needs to be added to the positive and negative electrolytes in time until they reach the initial state.

[0024] The capacity recovery method of the liquid flow battery electrolyte in the present invention reduces the liquid flow battery positive electrode electrolyte by discharging, replacing the conventional direct charging and reduction of the liquid flow battery positive electrode electrolyte, and recovers the active substance that plays a reducing role by charging, thereby realizing the recycling of the reducing active substance.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The recovery process of the electrolyte capacity of the flow battery in the present invention does not require the use of expensive catalysts, does not require the use of dangerous hydrogen as a reducing agent, the reaction process is mild, and the operation process is safe;

[0027] 2. The present invention does not introduce impurity ions into the positive electrolyte of the flow battery during the entire process of restoring the capacity of the flow battery. Only an appropriate amount of deionized water needs to be added. Therefore, the recovery method has no effect on the charge and discharge performance of the flow battery electrolyte.

[0028] 3. During the entire electrolyte capacity recovery process, only electricity and deionized water are consumed, and only oxygen is discharged. The reaction process is green, clean and efficient, which is beneficial to the cleanliness of the environment and the health and safety of the experimental operators. DETAILED DESCRIPTION

[0029] Example 1

[0030] The first step: construct a zinc deposition battery. The positive and negative electrodes of the zinc deposition battery do not need to be separated by a diaphragm, and the electrolyte is directly connected. The electrolyte is acidic and contains zinc ions and paired anions. The concentration of zinc ions is 2 mol / L, and the solvent is water. The positive and negative electrode materials are graphite.

[0031] Step 2: Zinc deposition. To charge the zinc deposition battery, connect the positive and negative electrodes of the DC power supply to the positive and negative electrodes of the zinc deposition battery respectively, and power on for electrolysis; oxygen evolution occurs at the positive electrode of the battery, and the generated oxygen is precipitated in the form of gas and escapes into the air, and will not continue to accumulate in the zinc deposition battery to cause overpressure; zinc evolution occurs at the negative electrode of the battery, and the precipitated zinc is deposited on the surface of the negative electrode in the form of a dense solid. When the total amount of zinc deposition reaches the designed capacity, zinc deposition is stopped.

[0032] The positive and negative electrode reactions and the overall reaction of the zinc deposition process are as follows:

[0033] Positive electrode: 2H2O-4e - →4H + +O2↑, E0=1.229V

[0034] Negative electrode: Zn 2+ +2e - →Zn↓, E0=-0.7618V

[0035] Overall reaction: 2Zn2+ +2H2O→2Zn↓+O2↑+4H + , E0=1.9908V

[0036] Step 3: Charge the iron-chromium flow battery. Charge the iron-chromium flow battery that needs to recover the electrolyte capacity, and measure the charge transfer amount of the positive electrode electrolyte before and after charging as the design capacity.

[0037] The positive and negative electrode reactions and the overall reaction during the charging process are as follows:

[0038] Positive electrode: Fe 2+ -e - →Fe 3+ , E0=0.77V

[0039] Negative electrode: Cr 3+ +e - →Cr 2+ , E0=-0.41V

[0040] Overall reaction: Fe 2+ +Cr 3+ →Fe 3+ +Cr 2+ , E0=1.18V

[0041] After charging is completed, the ion valence state of the positive electrode electrolyte of the liquid flow battery is tested and compared with the initial ion valence state of the positive electrode electrolyte of the liquid flow battery. The total amount of ions that need to be restored for rebalancing and the total number of charge transfers are calculated as the design capacity.

[0042] Step 4: Build a rebalanced battery. The positive electrolyte of the flow battery after charging in the third step is introduced into the positive electrode of the rebalanced battery, and the electrolyte after zinc deposition in the second step is introduced into the negative electrode of the rebalanced battery. The positive and negative electrolytes are separated by a proton exchange membrane. The proton exchange membrane needs to isolate the ions in the electrolyte of the zinc deposition battery from entering the positive electrolyte of the flow battery, thereby preventing the positive electrolyte of the flow battery from being contaminated and affecting the charge and discharge performance of the flow battery. The electrode after zinc deposition in the second step is used as the negative electrode of the rebalanced battery, and graphite is used as the positive electrode of the rebalanced battery.

[0043] Step 5: Discharge the rebalanced battery. Connect the discharge equipment to the rebalanced battery to discharge the rebalanced battery until it reaches its cut-off discharge condition. During the discharge of the rebalanced battery, the trivalent iron ions reacting at the positive electrode of the rebalanced battery and the generated divalent iron ions remain dissolved in the positive electrode electrolyte of the rebalanced battery; the zinc ions generated by the negative electrode reaction of the rebalanced battery dissolve into the negative electrode electrolyte of the rebalanced battery. At the same time, the hydrogen ions in the negative electrode electrolyte of the rebalanced battery pass through the proton exchange membrane into the positive electrode electrolyte of the rebalanced battery. The positive electrode of the rebalanced battery will undergo a reduction reaction from trivalent iron ions to divalent iron ions; the negative electrode of the rebalanced battery will undergo an oxidation reaction from zinc to zinc ions. The positive and negative electrode reactions and the overall reaction of the discharge process are as follows:

[0044] Positive electrode: Fe 3+ +e - →Fe 2+ , E0=0.77V

[0045] Negative electrode: Zn↓-2e - →Zn 2+ , E0=-0.7618V

[0046] Overall reaction: 2Fe 3+ +Zn↓→2Fe 2+ +Zn 2+ , E0=1.5318V

[0047] Step 6: Repeat steps 1 to 5 until the valence state of the positive electrolyte of the flow battery is restored to the initial state. After the cycle is completed, the positive electrolyte in the rebalanced battery is introduced into the positive electrolyte storage tank of the flow battery, and the difference between the liquid level of the positive and negative tanks of the flow battery and the initial state is calculated to determine whether deionized water needs to be added to the positive and negative tanks.

[0048] Example 2

[0049] Capacity recovery scheme of all-vanadium redox flow battery using anthraquinone-2,7-disulfonate disodium (AQDS).

[0050] Step 1: Construct an AQDS reduction battery. The electrolyte is an AQDS aqueous solution with a concentration of 5 mol / L, which is acidic, and the positive and negative electrolytes have the same composition. The positive and negative electrodes of the AQDS reduction battery need to be acid-resistant and have stable performance. There is no need for a diaphragm to separate the positive and negative electrodes of the AQDS reduction battery, and the positive and negative electrolytes can be directly connected. The positive and negative electrode materials are titanium plates.

[0051] Step 2: AQDS reduction. Charge the AQDS reduction battery, connect the positive and negative poles of the DC power supply to the positive and negative poles of the AQDS reduction battery respectively, and power on for electrolysis; oxygen evolution occurs at the positive electrode, and the generated oxygen is precipitated in the form of gas and escapes into the air, and will not continue to accumulate in the AQDS reduction battery to cause overpressure; AQDSH2 is generated at the negative electrode, and the generated AQDSH2 dissolves in the electrolyte. When the total amount of AQDS reduction reaches the designed capacity, stop AQDS reduction.

[0052] The positive and negative electrode reactions and the overall reaction of the AQDS reduction process are as follows:

[0053] Positive electrode: 2H2O-4e - →4H + +O2↑, E0=1.229V

[0054] Negative electrode: AQDS+2H + +2e - →AQDSH2, E0=0.21V

[0055] Overall reaction: 2AQDS+2H2O→2AQDSH2+O2↑, E0=1.019V

[0056] Step 3: Charge the flow battery. Charge the all-vanadium flow battery that needs to recover the electrolyte capacity until it reaches its cut-off charging condition. The positive and negative electrode reactions and the overall reaction of the charging process are as follows:

[0057] positive electrode: E0=1.004V

[0058] Negative electrode: V 3+ +e - →V 2+ , E0=-0.255V

[0059] Overall reaction: E0=1.259V

[0060] After charging is completed, the ion valence state of the positive electrode electrolyte of the liquid flow battery is tested and compared with the initial ion valence state of the positive electrode electrolyte of the liquid flow battery. The total amount of ions that need to be restored for rebalancing and the total number of charge transfers are calculated as the design capacity.

[0061] Step 4: Build a rebalancing battery. The positive electrolyte of the flow battery after charging in the third step is introduced into the positive electrode of the rebalancing battery, and the electrolyte after AQDS reduction in the second step is introduced into the negative electrode of the rebalancing battery. The positive and negative electrolytes are separated by a proton exchange membrane. The proton exchange membrane needs to isolate the ions in the electrolyte of the AQDS reduction battery from entering the positive electrolyte of the flow battery, thereby preventing the positive electrolyte of the flow battery from being contaminated and affecting the charge and discharge performance of the flow battery. Use titanium plates as the positive / negative electrodes of the rebalancing battery.

[0062] Step 5: Discharge the rebalanced battery. Connect the discharge equipment to the rebalanced battery to discharge the rebalanced battery until it reaches its cut-off discharge condition. During the discharge of the rebalanced battery, the pentavalent vanadium ions reacting at the positive electrode of the rebalanced battery and the tetravalent vanadium ions generated are always dissolved in the positive electrode electrolyte of the rebalanced battery; the AQDSH2 reacting at the negative electrode of the rebalanced battery and the AQDS generated are always dissolved in the negative electrode electrolyte of the rebalanced battery. At the same time, the hydrogen ions in the negative electrode electrolyte of the rebalanced battery pass through the proton exchange membrane into the positive electrode electrolyte of the rebalanced battery. The positive electrode of the rebalanced battery will undergo a reduction reaction from pentavalent vanadium ions to tetravalent vanadium ions; the negative electrode of the rebalanced battery will undergo an oxidation reaction from AQDSH2 to AQDS. The positive and negative electrode reactions and the overall reaction of the discharge process are as follows:

[0063] positive electrode: E0=1.004V

[0064] Negative electrode: AQDSH2-2e - →AQDS+2H + , E0=0.21V

[0065] Overall reaction: E0=0.794V

[0066] Step 6: Repeat steps 1 to 5 until the valence state of the positive electrolyte of the flow battery is restored to the initial state. After the cycle is completed, the positive electrolyte in the rebalanced battery is introduced into the positive electrolyte storage tank of the flow battery, and the difference between the liquid level of the positive and negative tanks of the flow battery and the initial state is calculated to determine whether deionized water needs to be added to the positive and negative tanks.

[0067] Example 3

[0068] Reference (ferrocenylmethyl)trimethylammonium chloride (FcNCl), in order to avoid Cl - Oxidation of FeIII and capacity recovery scheme for zinc-bromine flow batteries using (ferrocenylmethyl)trimethylammonium nitrate (FcNNO3(FeⅢ)).

[0069] Step 1: Construct a FcNNO3 (FeⅢ) reduction battery. The electrolyte is an FcNNO3 (FeⅢ) aqueous solution with a concentration of 0.001 mol / L. There is no need for a diaphragm to separate the positive and negative electrodes. The positive and negative electrolytes can be directly connected. The electrolyte composition is the same, and the positive and negative electrode materials are nickel plates.

[0070] Step 2: FcNNO3(FeⅢ) reduction. Charge the FcNNO3(FeⅢ) reduction battery, connect the positive and negative poles of the DC power supply to the positive and negative poles of the FcNNO3(FeⅢ) reduction battery respectively, and power on for electrolysis; oxygen evolution reaction occurs at the positive electrode, and the generated oxygen is precipitated in the form of gas and escapes into the air, and will not continue to accumulate in the FcNNO3(FeⅢ) reduction battery to cause overpressure; FCNNO3(FeⅡ) is generated at the negative electrode, and the generated FCNNO3(FeⅡ) dissolves in the electrolyte. When the total amount of FcNNO3(FeⅢ) reduction reaches the designed capacity, stop FcNNO3(FeⅢ) reduction.

[0071] The positive and negative electrode reactions and the overall reaction of the FcNNO3(FeⅢ) reduction process are as follows:

[0072] Positive electrode: 2H2O-4e - →4H + +O2↑, E0=1.229V

[0073] Negative electrode: FCNNO3(FeⅢ)+H + +e - →FCNNO3(FeⅡ), E0=0.61V

[0074] Overall reaction: 4FCNNO3(FeⅢ)+2H2O→4FCNNO3(FeⅡ)+O2↑, E0=0.619V

[0075] Step 3: Charge the flow battery. Charge the zinc-bromine flow battery that needs to recover the electrolyte capacity until it reaches its cut-off charging condition. The positive and negative electrode reactions and the overall reaction during the charging process are as follows:

[0076] Positive electrode: 2Br - -2e - →Br2, E0=1.087V

[0077] Negative electrode: Zn 2+ +2e - →Zn↓, E0=-0.7618V

[0078] Overall reaction: Zn 2+ +2Br - →Zn↓+Br2, E0=1.8488V

[0079] After charging is completed, the ion valence state of the positive electrode electrolyte of the liquid flow battery is tested and compared with the initial ion valence state of the positive electrode electrolyte of the liquid flow battery. The total amount of ions that need to be restored for rebalancing and the total number of charge transfers are calculated as the design capacity.

[0080] Step 4: Build a rebalanced battery. The positive electrolyte of the flow battery after charging in the third step is introduced into the positive electrode of the rebalanced battery, and the electrolyte after FcNNO3 (FeⅢ) reduction in the second step is introduced into the negative electrode of the rebalanced battery. The positive and negative electrolytes are separated by a proton exchange membrane. The proton exchange membrane needs to isolate the ions in the electrolyte of the FcNNO3 (FeⅢ) reduction battery from entering the positive electrolyte of the flow battery, thereby preventing the positive electrolyte of the flow battery from being contaminated and affecting the charge and discharge performance of the flow battery. Use nickel plates as the positive / negative electrodes of the rebalanced battery.

[0081] Step 5: Discharge the rebalanced battery. Connect the discharge device to the rebalanced battery to discharge the rebalanced battery until it reaches its cut-off discharge condition. During the discharge of the rebalanced battery, the Br2 reacted at the positive electrode of the rebalanced battery and the generated Br - It always exists in the positive electrode electrolyte of the rebalanced battery; the FCNNO3 (FeⅡ) and the generated FcNNO3 (FeⅢ) reacted at the negative electrode of the rebalanced battery are always dissolved in the negative electrode electrolyte of the rebalanced battery. At the same time, the hydrogen ions in the negative electrode electrolyte of the rebalanced battery pass through the proton exchange membrane into the positive electrode electrolyte of the rebalanced battery. The positive electrode of the rebalanced battery will undergo Br2 to Br - Reduction reaction; the oxidation reaction of FCNNO3 (FeⅡ) into FcNNO3 (FeⅢ) will occur at the negative electrode of the rebalanced battery. The positive and negative electrode reactions and the overall reaction of the discharge process are as follows:

[0082] Positive electrode: Br2+2e - →2Br - , E0=1.087V

[0083] Negative electrode: FCNNO3(FeⅡ)-e - →FCNNO3(FeⅢ)+H + , E0=0.61V

[0084] Overall reaction: 2FCNNO3(FeⅡ)+Br2→2FCNNO3(FeⅢ)+2Br - +2H + , E0=0.477V

[0085] Step 6: Repeat steps 1 to 5 until the valence state of the positive electrolyte of the flow battery is restored to the initial state. After the cycle is completed, the positive electrolyte in the rebalanced battery is introduced into the positive electrolyte storage tank of the flow battery, and the difference between the liquid level of the positive and negative tanks of the flow battery and the initial state is calculated to determine whether deionized water needs to be added to the positive and negative tanks.

[0086] Example 4

[0087] The zinc ion concentration in the zinc deposition cell is 3 mol / L, and the other conditions are the same as those in Example 1.

[0088] Example 5

[0089] The zinc ion concentration in the zinc deposition cell is 0.003 mol / L, and the other conditions are the same as those in Example 1.

Claims

1. A method for recovering the capacity of a flow battery, characterized in that: The following steps are involved: Charging flow batteries that require capacity recovery; Construct a reduction battery: the positive and negative electrodes are made of acid-resistant materials, the positive and negative electrodes of the battery are connected, the electrolyte contains a redox medium, and the solvent is water; Restore battery charge; Constructing a rebalancing battery: using the positive and negative electrodes of the reduced battery after charging or the same materials as the positive and negative electrodes of the reduced battery after charging as the positive and negative electrodes of the rebalancing battery, the electrolyte of the reduced battery after charging as the negative electrolyte of the rebalancing battery, and the positive electrolyte of the flow battery after charging as the positive electrolyte of the rebalancing battery, and the positive and negative electrolytes are separated by a proton exchange membrane; Connecting a discharge device to the rebalanced battery to discharge the rebalanced battery; The positive electrode electrolyte discharged from the rebalanced battery is introduced into the positive electrode of the flow battery.

2. The method for recovering the capacity of a flow battery according to claim 1, characterized in that: The redox medium is a redox couple that needs to meet the following three conditions at the same time: it does not react with other components in the flow battery electrolyte except the redox medium, the redox potential is lower than the positive electrode potential of the flow battery to be reduced, and the redox products will not penetrate the proton exchange membrane in the rebalancing battery.

3. The method for recovering the capacity of a flow battery according to claim 1, characterized in that: The redox mediator is selected from Zn / Zn 2+ ,Ni / Ni 2+ 、Pb / Pb 2+ 、AQDSH2 / AQDS、EV 0 / EV 2+ Or one of FcNNO3(FeⅡ) / FcNNO3(FeⅢ).

4. The method for restoring the capacity of a flow battery according to claim 1, characterized in that: The molar concentration of the redox medium in the electrolyte is 0.001-5 mol / L.

5. The method for recovering the capacity of a flow battery according to claim 1, characterized in that: The acid-resistant material is selected from one of platinum, palladium, silver, titanium, nickel, graphite, carbon nanotubes, diamond film, titanium oxide, nickel oxide, tin oxide, or a composite material composed of any two of the above.

6. The method for restoring the capacity of a flow battery according to claim 1, characterized in that: When the reduction battery is charged, oxygen is released from the positive electrode and the redox medium at the negative electrode undergoes a reduction reaction.

7. The method for recovering the capacity of a flow battery according to claim 1, characterized in that: The liquid flow battery is selected from one of an all-vanadium liquid flow battery, an iron-chromium liquid flow battery or a zinc-bromine liquid flow battery.

8. The method for restoring the capacity of a flow battery according to claim 1, characterized in that: The liquid flow battery is charged, the ion valence state of the positive electrode electrolyte is tested before and after charging, and the total amount of charge required to be transferred for rebalancing is calculated as the design capacity; When the total amount of charge transferred during the charging process of the reduction battery reaches the designed capacity, stopping the electrolysis; When the total amount of charge transferred during the discharge process of the rebalanced battery reaches the designed capacity, the discharge is stopped.

9. A device for implementing the method for restoring the capacity of a flow battery according to any one of claims 1 to 8, characterized in that: It includes three parts: a reduction battery, a rebalancing battery and a liquid flow battery. The reduction battery electrolyte is connected to the negative electrode of the rebalancing battery through a pipeline, and the positive electrode electrolyte of the liquid flow battery is connected to the positive electrode electrolyte of the rebalancing battery through a pipeline. The above pipelines are controlled by valves.

10. Application of the method for recovering the capacity of a liquid flow battery according to any one of claims 1 to 8 or the device according to claim 9 in the field of liquid flow batteries.